The invention relates to a device for generating an offset of transported flexible sheet material, especially sheets of paper, with a feeding and a discharging transport path section and a transport path section which is assigned to the offset generating means.
One device for producing an offset can be used to deposit offset a certain number of sheets at a time in a delivery stack of a printing machine in order, for example, to separate the sheets of one job from another. But this offset can also be used to correct the deposition of individual sheet materials with respect to the exactness of the position in order to obtain a perfect delivery stack. There are devices of the initially mentioned type in the most varied versions. Side stops, crossover conveyor means with rollers or balls which are located transversely to the transport direction or slantwise to it or with transversely movable drums have been proposed. DE 43 13 840 C1 is named by way of example for the latter proposal.
These proposals generally require complex control and often return of the offset generating device which is made as a crossover conveyor means to its original position, as is the case in the subject matter of DE 43 13 840 C1. Many of these proposals are not independent of the paper format; this necessitates detection and consideration of the format.
Therefore the object of the invention is to make available an easily adjustable device for generating an offset of transported flexible sheet material which works without the reset requirements and independently of format. The object is achieved by the offset generating device having at least two deflections which are parallel and which work in opposite directions and which can be moved to an angle xcex3 to the transport direction; this angle is measured in the plane of the feeding transport path section and is not equal to 90xc2x0 projected onto this plane. The latter relates to the deflections which do not lie in the plane of the feeding transport path section.
In the approach in the invention it is possible to achieve a certain offset by setting a certain angle. In doing so the offset generating device is swiveled out of its initial position, in which the angle xcex3 to the transport direction of the material is 90xc2x0, by an angle xcex1 in one direction or the other, depending on in which direction the material is to be displaced. A control means is not necessary for this purpose, since an offset caused thereby can be directly assigned to the angle. It is therefore enough to calibrate the angle setting with the amount of assigned offset. With this device, within a wide area for which the device can be used with respect to its size, flexible sheet materials can be displaced regardless of their format with respect to the location of their side edges without the need to set the device to the different formats. There is no need to reset the offset generating device after each sheet since the offset generating device works continuously. This also makes it possible to generate an offset not only in sheets, but also continuous webs. Since the mechanism need not be continually reset, it is simpler and less susceptible to problems.
Since it is generally a matter of displacing sheets of a material, the invention proposes that pairs of guide elements are arranged such that the sheets are always held and transported on both sides by at least one pair of guide elements. They can be held either on the outside edges, over the entire width or over the entire surface. If the device is made such that the feeding and discharging transport path sections do not lie on parallel planes, both parallel and also angular offset is achieved; the latter is dependent on the angular position of the planes. But the normal case is that a parallel offset is desired for one of the initially mentioned purposes. Therefore it is proposed that the feeding and discharging transport path sections lie on parallel planes.
One feasible embodiment of the invention calls for the offset generating device to be made as a unit which can be swiveled by an angle xcex1. Regardless of the specific configuration of the offset generating means, joint swiveling of all of the parts which must be swiveled to generate the offset can be done.
One embodiment calls for there to be two deflections, one deflection working opposite the other. These two deflections can be made as arc-shaped guides. Here it is possible for the two deflections to be lined up in succession in an S shape or there can be a flat transport path between the two deflections.
One alternative embodiment calls for there to be several deflections, at least two deflections deflecting in the first direction and at least two deflecting in the opposite direction. This configuration has the advantage that less dramatic deflections are necessary. This is advantageous especially for flexible materials such as cardboard. But a similar effect is also achieved by the arc-shaped guides having a correspondingly large radius.
One possible embodiment calls for the transport path section assigned to the offset generating device to have a flat surface which lies between the deflections and which runs at an angle xcex2 of 90xc2x0 to the other transport path sections. In this embodiment the greatest offset is produced by adjustment by an angle xcex1 to the transport direction. Here the amount of offset is dependent not only on the angle xcex1, but also on the distance h of the plane of the feeding transport path section to the plane of the discharging transport path section. The offset which can be produced is likewise increased by enlarging the indicated surface which extends perpendicularly vertical.
Another embodiment calls for the transport path section assigned to the offset generating device to have a surface which lies between the deflections and which runs at an angle xcex2 of less than 90xc2x0 to the other transport path sections. This embodiment of the transport path of offset generating device as a slanted plane on the one hand leads to the attained offset becoming less, but on the other hand this has the advantage that the deflections take place at an obtuse angle and thus also less flexible material can be displaced by the device, as is the case for example for thick paper or cardboard. Here a combination with several deflections or with deflections with large radii is possible.
There are various possibilities for the configuration of the deflections. One proposal calls for the guide of the sheet material to consist of several pairs of rollers, some of the pairs of rollers being made as pairs of guide rollers and some of the pairs of rollers being made as pairs of deflection rollers and at least the latter with respect to their angle to the transport direction can be moved to an angle xcex1 which is not equal to 90xc2x0. In this embodiment the pairs of rollers must be packed relatively tight and may have only so little angular offset that the material is always securely gripped by the next pair of rollers as it continues to be transported.
Another embodiment calls for the offset generating device to be made with deflections as the guideway with a guide gap between the guide surfaces. It can also be provided here that at the start and at the end of the guideway there is a pair of guide rollers which is used to convey the material by the guideway. These pairs of guide rollers can then be assigned to the offset generating device or the feeding transport path section or the discharging transport path section. The guideway can be sheet metal sections which can be made S shaped, also with a straight section, therefore a surface between the curves. The guideway can of course be composed of all possible materials which have low friction relative to the material to be transported and which can be made with a very smooth surface. For example, the guideway can be made as an aluminum extruded section and can have a special sliding surface of the guide surfaces.
Since there must be guide rollers for transport of the material within the transport path and they may not lie farther apart in their distance than the length of the material, it can be useful to provide at least one pair of guide rollers within the guideway. Feasibly there are so many pairs of guide rollers with a drive in the guideway of the offset generating device that the smallest formats to be processed are still securely grasped. At least one pair of guide rollers is used, but preferably all pairs of guide rollers as pairs of drive rollers are used for delivering sheets of sheet material in the area of the offset generating means. This configuration also allows a large offset for small sheets.
Since the transported sheet material is likewise arranged obliquely due to the slanted position of the offset generating device with respect to the front edge and the rear edge, it is useful if the pairs of guide rollers or the pair of guide rollers is set accordingly. Therefore it is proposed that at least one pair of guide rollers of the offset generating device can be inclined such that the slanted position of the pair of guide rollers corresponds to the slanted position of the front edge of the sheet of the material to be displaced laterally at the site of this at least one pair of guide rollers. This can result in that the front edge of the material is grasped and transported at the same time by two or more rollers and thus an unwanted inclination by failure to grip the front edge of the material at the same time by the pairs of drive rollers or one pair of drums is prevented. This inclination in turn corresponds to the angle xcex1 with which the offset generating device is set to produce a certain offset.
One specific embodiment of the inclination of one pair of guide rollers calls for a bearing which carries the pair of guide rollers to be supported in the middle area to be able to swivel on the offset generating device and for a swiveling mechanism for achieving the inclination of the pair of guide rollers to link its swiveling to the swiveling of the offset generating device by the angle xcex1. This can lead to the front edge of the material being gripped and transported by two or more rollers at the same time and thus unwanted inclination due to failure to grip the front edge of the material at the same time by the pairs of drive rollers or one pair of drums being prevented. The swiveling mechanism can be made in different ways. One proposal calls for the swiveling mechanism to be a connecting rod which on the one hand is coupled to the bearing of the pair of guide rollers and on the other to a holder which is mounted on the machine housing, the coupling to the bearing being remote from its axis of rotation in order to achieve swiveling of the bearing around the axis of rotation.
Preferably the swiveling mechanism is made such that the respective pair of guide rollers with the inclination is simultaneously displaced laterally such that this offset corresponds to the offset of the material which the latter already has in the area of the pair of guide rollers. This results in that the material is always held and guided on its edge areas. This is used for reliable guidance and careful handling of picture areas when the material is printed. One proposal for a practical version calls for the bearing of the guide rollers to be supported by a swiveling lever which is coupled to the offset generating means.
Feasibly the aforementioned roller pairs are made such that can be set to the width of the material. In this way it is possible to take into account any format width in an optimum manner. Alternatively the rollers can also be made as drums which have the maximum format width, thus it is not necessary to change the setting when the format changes.
Alternatively to the transport of material by rollers or by a guideway, it can also be provided that the device has at least one transport belt. The advantage of these transport belts is that any type of material is reliably guided regardless of its size. Here it is provided that the device has at least one pair of transport belts which interact such that the material can be transported between them. Thus it is possible for the material which is to be displaced to be securely and carefully held and guided since it need not slide on surfaces. Moreover these transport belts can be used for much larger variations with respect to format size since it is irrelevant whether a large or a small format is running through the transport belts.
The transport belts can be made such that one pair of transport belts is used for feed, an angularly adjustable pair of transport belts is used to produce the offset and one pair of transport belts is used for discharge.
In all these approaches, inclining the offset generating device produces an angular gap which must be bridged by the sheet material which is to be transported. Therefore it can often be a good idea for there to be transition guides on the transition from the feeding transport path section to the offset generating device and on the transition from the latter to the discharging transport path section. These transition guides must be made such that they keep up with the angular adjustments in the intended angular range. For example, the transition guide can consist of bars which on one side have a swivel coupling and on the other side a slideway. The latter can be suspended with a swiveling capacity or can be made such that the bars can swivel into it. Of course other configurations are conceivable which keep up with the swiveling motion, for example metal sheets which are fixed on one side and are supported in a slideway on the other.
One especially advantageous embodiment calls for the pair of transport belts to extend over all transport path sections, one pair of rollers at a time being located on the ends of the two transport belts for guiding and driving and in between there being an offset generating device which acts on the pair of transport belts and at least one of the pairs of rollers being made such that it accommodates the resulting offset of the transport belts. This configuration is based on the finding that one such transport belt behaves exactly like a sheet guided by one such offset generating device and likewise has an offset which is dependent on the angular position of the offset generating means. Since the pair of transport belts thus has the same offset as the offset of the material on one side, i.e. the side on which the material leaves the device for generating the offset, the pair of rollers there must be made to accommodate the offset. Either the roller pair has a correspondingly greater width than the transport belt or it is a pair of rollers which can be moved on one axis. For example, they can be rubber rollers which have high friction relative to the transport belt, the rubber rollers being guided on axles and being made such that they can be pushed with little force, therefore have a bearing which can be pushed on the axes with little force. These pairs of rollers then adjust themselves according to the adjusted offset with respect to their lateral position.
In this embodiment there are also various possibilities for impressing the desired offset onto the transport belts by means of the offset generating means. One embodiment calls for the offset generating device to consist of at least two guide surfaces which impress deflections on the transport belts. In this embodiment there is friction between the transport belts and the guide surfaces, but the friction can be kept correspondingly low by a corresponding configuration and material choice of the guide surfaces and the transport belts and it is possible to provide the guide surfaces with relatively gentle deflections, therefore with large radii, and thus to achieve careful directional deflection of the transport belts and also of the materials.
Another embodiment of the offset generating device which acts on the pairs of transport belts consists in at least two rotary elements which are arranged such that they impress at least two deflections on the transport belts. The advantage of this embodiment is that the rotary elements have only very little or no friction against the transport belts and that therefore wear is kept low. There can be two or more rotary elements. Here it is possible to provide two relatively large deflection rollers, one for each deflection. In this way more careful deflection of the materials is achieved. Alternatively there can also be several smaller drums which undertake the deflections in two or more stages which thus take place at several flat angles.
The transport belts can also be made differently; they can be several belts guided in parallel or it is possible to use one wide flat belt per transport belt.